Isoform 4 of Serine/threonine-protein phosphatase 2A 56 kDa regulatory subunit gamma isoform

PPP2R5C encodes the 56 kDa regulatory subunit gamma of protein phosphatase 2A (PP2A), a serine/threonine phosphatase complex component. This isoform (Q13362-4) is a 540-amino-acid variant of approximately 62.8 kDa. PP2A regulatory subunits modulate the catalytic activity and substrate specificity of the phosphatase holoenzyme, which plays roles in cell signaling, protein dephosphorylation, and regulation of kinase cascades (UniProt: Q13362-4).

PPP2R5C is widely expressed across tissues and participates in fundamental cellular phosphorylation pathways. The protein is involved in diverse signaling contexts where PP2A activity is required for proper cellular homeostasis and regulation of protein kinases implicated in neuronal function.

In Alzheimer's disease, PPP2R5C isoform 4 is significantly downregulated in post-mortem AD brain tissue compared to age-matched controls, with a mean log2 fold-change of −1.10 (Chaparral AD proteomics). This reduction was detected via TMT-labeled quantitative proteomics across subcellular fractions of human brain tissue, suggesting potential impairment of PP2A-mediated phosphatase signaling in the AD brain proteome.